Threaded inserts are used in a variety of situations to provide a reliable threaded hole for a fastener. For instance, threaded inserts are used in workpieces that are too soft to provide reliable threads, in workpieces that are too thin to accept threads, or in a workpiece with damaged or stripped threads. The threaded insert can be inserted into an opening in such a workpiece so that the workpiece can still receive a threaded fastener.
A particular variety of threaded insert is a helical insert, which can be seen in prior art FIG. 8. As can be seen in the semi-sectional portion of FIG. 8, the helical insert 10 is a coil of wire that typically has a diamond or hexagonal shaped cross-section such that exterior and interior v-shaped edges are created on the insert. In that way, when the coil is compressed, the cross-section allows the exterior set of v-shaped edges 13 to engage the workpiece 14 (not shown). The inner set of v-shaped edges 15 then serves as the threads to receive a threaded fastener. The downstream end of the helical insert 10 features a medially projecting tail 17, referred to as a tang. The tang 17 aids in installation of the helical insert. On the final coil of the helical insert, proximal to the tang 17, is a notch 19. As described below, the notch 19 allows the tang 17 to be removed after installation of the helical insert.
Installation of a helical insert on a manufactured part is typically accomplished in four steps. First, the receiving hole is drilled into the workpiece. Second, threads for receiving the helical insert are tapped into the hole. Third, the helical insert is installed in the workpiece using an installation tool. The installation tool is a cylindrical rod having a diameter of a size to accommodate the helical insert. The end of the installation tool has a stepped surface to engage and drive the tang of the helical insert during installation, and the portion of the installation tool immediately superior to the end has threads to receive the helical insert. In the installation step, the helical insert is wound onto threads at the end of the installation tool until the tang contacts the flat end of the tool. Then, the installation tool is inserted into the hole in the workpiece and rotated in a first direction to feed the helical coil into the hole until the proper depth is achieved. Then the installation tool is rotated in a reverse direction to release the helical insert in the hole. In the final step, another tool having a diameter smaller than the diameter of the helical insert is inserted through the helical insert until it contacts the tang. A hammer is used to strike the tool, which breaks the tang from the helical insert at the location of the notch.
When manufacturing parts that require a helical insert, correctly installing the helical insert into the part is important to assure the quality of the final product. When working on a high volume of parts, a significant number of those parts can fail to contain a helical insert or fail to have the tang removed from the helical insert. Such part defects can cause delays and increased costs for customers, who have to spend time and money to fix these parts or order new ones.
Thus a need exists in the art for a device that a manufacturer can use to check the quality of manufactured parts that include helical inserts.